Family members recently flew BOS-DUB-LHR on a single Aer Lingus ticket (short layover in DUB). They reported that they were asked to re-clear security at DUB, but that they were never asked to re-check their bags in DUB.

At LHR, they just got their bags and left from the "arrivals from Ireland and the U.K." area.

Where were they supposed to transit customs?